Abstract
Emerging threats of climate change require the rapid development of improved varieties with a higher tolerance to abiotic and biotic factors. Despite the success of traditional agricultural practices, novel techniques for precise manipulation of the crop’s genome are needed. Doubled haploid (DH) methods have been used for decades in major crops to fix desired alleles in elite backgrounds in a short time. DH plants are also widely used for mapping of the quantitative trait loci (QTLs), marker-assisted selection (MAS), genomic selection (GS), and hybrid production. Recent discoveries of genes responsible for haploid induction (HI) allowed engineering this trait through gene editing (GE) in non-inducer varieties of different crops. Direct editing of gametes or haploid embryos increases GE efficiency by generating null homozygous plants following chromosome doubling. Increased understanding of the underlying genetic mechanisms responsible for spontaneous chromosome doubling in haploid plants may allow transferring this trait to different elite varieties. Overall, further improvement in the efficiency of the DH technology combined with the optimized GE could accelerate breeding efforts of the major crops.
Highlights
Gene editing (GE), through the application of designed endonucleases, rapidly advances our understanding of gene function and regulatory elements involved in gene expression, as well as allows the engineering of DNA from base pair and to the chromosome level
The F1 hybrids were restored through crossing of the complementing Doubled haploid (DH) lines. It remains to be shown whether reverse breeding can be applied to crops; the availability of haploid induction (HI) lines in maize, wheat, and rice [57,58,59] suggests that it is a matter of time when we see this technology used in other species
Trait mapping is of particular importance to breeders, and generating a segregating DH population from F1 hybrids for marker–trait association studies has become common in barley, where efficiency of DH production is relatively high [60]
Summary
Gene editing (GE), through the application of designed endonucleases, rapidly advances our understanding of gene function and regulatory elements involved in gene expression, as well as allows the engineering of DNA from base pair and to the chromosome level (reviewed in [1]). DH protocols have been developed for more than 200 plant species [14] Another culture and wide hybridization are considered the most widespread techniques for generating DH lines in crops (Figure 1). The F1 hybrids were restored through crossing of the complementing DH lines It remains to be shown whether reverse breeding can be applied to crops; the availability of HI lines in maize, wheat, and rice [57,58,59] suggests that it is a matter of time when we see this technology used in other species. Trait mapping is of particular importance to breeders, and generating a segregating DH population from F1 hybrids for marker–trait association studies has become common in barley, where efficiency of DH production is relatively high [60]. At the same time, when a recessive mutation is lethal in a homozygous state, the DH system will not be suitable for such genetic analysis [20]
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